Microsoft KB Archive/101944

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Article ID: 101944

Article Last Modified on 8/5/2004


  • Microsoft Visual Basic 2.0 Professional Edition
  • Microsoft Visual Basic 3.0 Professional Edition

This article was previously published under Q101944


A new version of the MSCOMM.VBX control is available. This new control fixes a problem where the OnComm event will not fire when communicating with some 14.4K baud modems.


The following files are available for download from the Microsoft Download Center:

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to Obtain Microsoft Support Files from Online Services

Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.
The date, time, size, and version number of the MSCOMM.VBX file that shipped with Visual Basic version 3.0 is:

   Date: 28-APR-1993
   Time: 12:00 a.m.
   Size: 34304
   Version: 2.0.9000.7

The date, time, size, and version number of the updated MSCOMM.VBX file is as follows:

   Date: 12-MAY-1993
   Time: 12:21 p.m.
   Size: 34816

When using the MSCOMM.VBX provided with Visual Basic version 2.0 or 3.0 to communicate with a 14.4K baud modem, the OnComm event may not fire. The revised version of the MSCOMM.VBX control available fixes this problem by introducing a new Notification property. The problem relates to using Windows version 3.1 event driven communications. The new property fixes the problem by allowing you to use Windows version 3.0 polling techniques instead.

The Notification property is not available at design time, but you can get and set its property value at run time. It's default value of zero (0) tells the control to use Windows version 3.0 polling techniques. A value of 1 tells the control to use Windows version 3.1 event driven communications.

Microsoft recommends that you set the property value to 1 if you are using the MSCOMM control to communicate with a modem that has a baud rate lower than 14.4K baud.

One other change was made. The default property setting for the Interval property was changed from 1000 to 55.


To install the new control, copy the updated version to the WINDOWS\SYSTEM directory on your computer. Also check to make sure that no other copies of MSCOMM.VBX exist on your computer. If you find an older version of the MSCOMM.VBX file, delete it or rename it.
NOTE: When installing the updated MSCOMM.VBX, make sure no existing Visual Basic applications that used the original MSCOMM.VBX are broken. The updated MSCOMM.VBX (Version: is not compatible with Visual Basic application .EXE files compiled with the original version of the MSCOMM.VBX (Version: 2.0.9000.7). These applications must be recompiled with the version of the MSCOMM.VBX in order to work correctly with this updated .VBX file. The updated version of MSCOMM.VBX fixes a problem where the OnComm event will not fire when communicating with some 14.4 baud modems. If the specific problem fixed by the updated MSCOMM.VBX is not a concern and there are existing Visual Basic applications for which the source code is not available, use the original MSCOMM.VBX -- not the updated one.

Additional query words: kbfile update3.00 softlib S14642

Keywords: kbinfo kbdownload kbfile KB101944